The muscles of the pelvis relax due to the release of the hormone relaxin. This softens the pelvis and stretches it in preparation for delivery of the baby. Several joints, especially in the spine, become less stable and show signs of separation and movement to accommodate the growing baby.

The back muscles have additional strain added to them, causing some of the low back pain often experienced during pregnancy. In a non-pregnant woman the centre of gravity is located just in front of the spine and level with the kidneys. In a pregnant woman the centre of gravity is shifted forward, straining the spine and throwing her off-balance.

This may cause her to throw back her shoulders, lean backward on her heels, and place additional strain on her lower back. The ligaments, which add support and strength, are weakened, so she relies only on the muscles of her back to stand upright. The back muscles can become tight and tired, which can lead to low back pain.

When an employee tells their employer they’re pregnant, the employer should assess the risks to the woman and her baby. An ergonomic risk factor is any imbalance between the worker and the work environment that results in extra demands on the worker.

To reduce the risk of injury, ergonomic risk factors should be identified and reduced as much as possible. These are the main ergonomic risk factors during pregnancy:

• awkward postures;
• high force (e.g. heavy lifting);
• no rest;
• repetitive work.

Working in unfavourable conditions may have adverse effects on the woman and her baby.

The pregnant worker is at her greatest risk of injury during her third trimester when her abdomen is biggest. The amount of stress on the lower back is greater when an object carried or lifted is further away from the lower back due to the increased size of the abdomen. The further away from her body a woman has to carry an object, the lighter it must be.

Workstations should be adjustable to reduce any awkward postures and to accommodate the pregnant woman’s changing body. Women in jobs where they sit a lot may develop low back pain which may be relieved with the use of a proper chair with a supporting, adjustable back rest, as well as a footrest.

Due to body postures changing rapidly during pregnancy, sitting support and angles of chairs may need to be adjusted regularly to ensure the best support is provided to the pregnant worker. This is why having an adjustable chair
is so important.

Workers whose work is physically strenuous are at increased risk when pregnant. Physically strenuous work includes prolonged standing for more than three hours per day, working on industrial machines, repetitive heavy lifting, assembly line jobs and working in cold, hot or noisy environments. Where there are risks, the employer should take reasonable steps to remove them by offering the employee different work or changing her hours.

Postures that would further weaken and stretch her muscles, such as leaning forward at the waist, should be avoided during the pregnancy. Any necessary lifting, particularly during the latter stages of pregnancy should be performed with great care. With the growing abdomen, the low back is more vulnerable to injury and the baby’s health is at more risk due to straining of the abdominal muscles.